Re: How Alternators are "Upgraded"
Post by
BCjohnny » Sat Nov 22, 2014 6:34 am
<snip>
"Within a given frame size, simplistically, by increasing the cross sectional area of the conductor, in this case the stator windings, the amperage output is similarly increased. This can be done by increasing the number of turns of wire but more commonly by increasing the gauge with round section wire, or less commonly, going to 'flat-wound' large section wire (CAV, Denso etc). 'Re-wiring' the stator, for instance going from a star to delta wound arrangement, are other tricks manufacturers resort to, as is adding a 'tap' to star connected stators to create a four wire rectifier (~10%).
Upping the rotor magnetic field strength, again by increasing the number of turns, or increasing the field current, as Delco did with some european models by going from a 3amp to 7amp field, also give greater output to a lesser extent, as does reducing the rotor/stator air gap (obvious production limitations). Increasing the rotor diameter and 'slimming down' the stator width to maintain frame size, as Bosch did with certain 70/80amp K1s, is also an option.
Drawbacks..........As alternator efficiency is fairly constant across the better contemporary manufacturers, although in all cases goes down with machine temperature (alternators are most commonly rated 'hot'),
increasing the output creates more 'waste' heat, which affects all components, but the rectifier to the greatest extent. Higher rated diodes, more efficient heatsinking, and cooling flow are required. In this last respect modern internal fan (IV) machines which cool from the inside out, as opposed to older front fan draw through types, are better capable of dealing with this. Or, as OE outputs grow, jacketed machines plumbed it into the cooling system are becoming more common. Increasing field strength means higher rated parts.
Also, again within a given frame size, increasing ultimate output is usually at the expense of lower speed output. Much like a highly tuned engine, the power curve is more peaky. The 'cut-in-speed' (CIS), when the machine starts charging, is often higher too."<end snip>
